Figure 52

Fig. 52: Dispersion relation of the energy position parameter h as a function of Q at the indicated temperatures. The h parameter has been obtained fitting the inelastic part of the IXS data to a damped harmonic oscillator model. The excitation values have been scaled by the factor c_o(278 K) / c_o(T), with c_o(T) obtained from the equation-of-state. This has been done to emphasise in the same plot the departure of the dispersion relation from the c_o(T) law, shown by the solid line, which is valid in the Q 0$ limit. This figure demonstrates that, in the dispersion relations, the transition from c_o to c takes place at increasing Q values with increasing temperatures.